The invention relates to a joint yoke for a universal joint and also to a universal joint comprising the same.
U.S. Pat. No. 5,647,799 describes a universal joint having a joint yoke which comprises a longitudinal axis. The joint yoke comprises a base portion centered on the longitudinal axis, from which two yoke arms extend. These are arranged off-set in opposite directions from the longitudinal axis. Each yoke arm comprises a support bore. The support bores of both yoke arms are arranged on a common bore axis which extends at a right angle to the longitudinal axis. Each yoke arm has two arm portions which are formed integrally with the base portion and project therefrom. The two arm portions are separated by the support bore and have end faces distanced from the base portion. In each of these end faces, respectively, a threaded bore is arranged. Furthermore, each yoke arm comprises a bridge element which connects its two arm portions and has abutment faces formed in correspondence with the end faces and by which the bridge element abuts the two end faces of the arm portions and which bridge element is fastened by means of screws. For this, the bridge elements have respectively in the abutment faces a through bore, through which a threaded headed screw can be screwed into the threaded bore of the corresponding arm portion.
Such joint yokes and therefore, also universal joints, which have these joint yokes, are designed for a specific torque range. For high torques, as they for example are present in drives of rolling mills, bridge elements can be provided which are attached by more than one screw on the corresponding arm portion. The rotational diameter of such joint yokes is however limited, as in the assembled condition, only a small space is available. Because of this reason, as high as possible torque capacity has to be achieved. This means that for a joint yoke, as large as possible bearing bush has to be provided, because of which the support bore has to be formed correspondingly large. This means that the size of the bridge element, and, therefore, also the size of the end faces, are dependent on the one side on the size of the support bore and on the other side on the rotational diameter. Therefore, the connection between the bridge element and the arm portions are of special importance.
The invention has the object to provide a joint yoke which has a high torque capacity.
The object is solved according to the invention by a joint yoke for a universal joint comprising:
a longitudinal axis,
a base portion, centered on the longitudinal axis,
two yoke arms,
off-set in opposite directions from the longitudinal axis,
having, respectively, a support bore, wherein the support bores have a common bore axis, extending at a right angle to the longitudinal axis,
having, respectively, two arm portions integral with the base portion, separated by the support bore and having end faces, distanced from the base portion, with at least two threaded bores, which centers, respectively projected onto the bore axis of the neighboring support bore, are arranged with different distances to the longitudinal axis, wherein the threaded bore, arranged with the largest distance to the longitudinal axis, has a larger diameter than the other threaded bores,
having, respectively, a bridge portion, connecting the two arm portions and provided with abutment faces formed correspondingly to the end faces and in which through bores are arranged, which are formed and arranged in correspondence to the threaded bores,
screws, serving for the attachment of the bridge elements on the arm portions of the yoke arms and adapted to the threaded bores and the through bores.
Advantageous in this embodiment is that the screws arranged, when projected onto the bore axis, furthest away from the longitudinal axis ensure that the torque capacity is remarkably increased compared to an arrangement in which the screws and, therefore, the threaded bores have the same diameter.
Another advantage is that because of the fact that the threaded bores are arranged in reference to the bore axis closer to the longitudinal axis, and, therefore, also the corresponding screws are formed smaller, the angularity of the two joint yokes of a universal joint towards each other can be increased. Thus, with the same layout, a larger bending angle can be achieved.
In a further embodiment of the invention, it is provided, that the end faces of the arm portions and the abutment faces of the bridge elements are provided with a toothing. Preferably, its teeth extend parallel to the bore axis. Because of this, the connection between the two arm portions via the bridge element is further improved, as the arm portion which, depending on the rotational direction, is not loaded is stronger involved in the transmission.
In the case that three threaded bores are provided, it is possible, to form two of the threaded bores with the same diameter, while the third threaded bore which is arranged, when projected onto the bore axis of the neighboring support bore, in the end face furthest away from the longitudinal axis, has a larger diameter. In case that three threaded bores are provided, then it is also possible to form all with different diameters. All three threaded bores can be arranged with different distances when projected onto the bore axis of the neighboring support bore to the longitudinal axis. In a further embodiment of the invention, it is provided that per end face, the threaded bore which has the largest diameter has the smallest distance to the bore axis.
Furthermore, the threaded bores provided per end face can be arranged all with different distances to the bore axis.
Preferably, the threaded bore which is arranged, when projected onto the bore axis of the neighboring support bore, with the largest distance to the longitudinal axis, is increased by 1% to 35% compared to the next smaller threaded bore, whereby an immense increase in the transmissibility can be achieved. When, for example, this threaded bore is increased in size by around 20% in diameter compared to the next smaller threaded bore, an increase in the torque capacity of more than 20% compared to an arrangement, in which all threaded bores of an end face have the same diameter, can be achieved.
The object according to the invention is also solved by a universal joint which comprises a first joint yoke, which is formed according to one or more of the features of the joint yoke according to the invention, a second joint yoke, and a journal cross connecting the first joint yoke and the second joint yoke.
Preferably, the second joint yoke is also formed like the first joint yoke according to the features of the joint yoke according to the invention.